1. Field of the Invention
The present general inventive concept relates to a hard disk drive (HDD), and more particularly, to a method of searching to find a servo pattern recorded in a partial area of a disk in order to copy the servo pattern to another area of the disk.
2. Description of the Related Art
An HDD is a data storage device used in personal computers (PCs), MP3 players, mobile phones, etc. Data is recorded in concentric tracks on the surface of a magnetic disk, which is a data storage medium of the HDD. The disk is rotated at high speed by a spindle motor, and data is read and written by a magnetic head.
HDDs are manufactured through a mechanical assembly process, a servo write process, a function test process, and a burn-in test process, and are then available on the market after a final test process for checking whether defect correction is performed correctly. The mechanical assembly process is the process of assembling the mechanical parts of an HDD, the servo write process is the process of recording a servo pattern for servo control of an actuator on a disk, the function test process is the process of testing whether the combined mechanical and electrical parts of the HDD match each other and operate normally, and the burn-in test process is the process of searching for existing defects on the disk and allowing the defects to be avoided so that operational errors do not occur when the HDD operates.
In a conventional servo write process, a servo pattern is recorded in the entire recordable area of a disk using a servo writer. However, the conventional method takes a long time and is difficult to apply simultaneously to a plurality of HDDs, resulting in an increase of manufacturing cost. Thus, a method of recording a servo pattern in an entire recordable area of a disk by recording the servo pattern in a partial area of the disk using a servo writer, and copying the recorded servo pattern to a plurality of other recordable areas of the disk based on the original servo pattern has been developed. Hereinafter, a process of copying a servo pattern to a plurality of recordable areas based on a servo pattern recorded in a partial area is denoted as a servo pattern copy process, and the partial area is denoted as a servo pattern copy start area.
FIG. 1 is a diagram illustrating a conventional servo pattern search method corresponding to a servo pattern copy.
Referring to FIG. 1, prior to the servo pattern copy process, a servo pattern is recorded in tracks of a partial area of a disk 10 using a servo writer, and a spiral seed pattern AP required to perform the servo pattern copy process is recorded on tracks of an intermediate area M1. The servo pattern is recorded in the area around the outer circumference of the disk 10, which is a servo pattern copy start area C1.
In order to perform the servo pattern copy process, when an HDD is turned on, a magnetic head embedded in a head slider 27 searches for the servo pattern recorded in the servo pattern copy start area C1, and if the servo pattern is found in the servo pattern copy start area C1, the magnetic head performs a servo pattern copy process to the intermediate area M1. The servo pattern search process is performed as follows. When a current is applied to a voice coil 30 of an actuator 20, a swing arm 22 of the actuator 20 rotates clockwise around a pivot bearing 23 so that the head slider 27 moves from a parking area P1 to the outer circumference of the disk 10, as illustrated by a large arrow in FIG. 1. Thereafter, the swing arm 22 rotates counter-clockwise at a sufficiently low angular speed so that the magnetic head embedded in the head slider 27 can search for the servo pattern while the head slider 27 slowly moves over the servo pattern copy start area C1 towards the inner circumference of the disk 10.
The current applied to the voice coil 30 is determined using an open loop control method. However, since the electrical characteristics of the parts of an HDD can vary slightly with manufacturing tolerances, the head slider 27 frequently moves at an inappropriate speed to search for the servo pattern, instead of moving at a set speed. This can cause the head slider 27 to contact and damage the disk 10 when the actuator 20 rapidly crashes into a crash stop 50, or may delay the servo pattern search process if the magnetic head moves over the servo pattern copy start area C1 too quickly or too slowly.